Difference between RDS Multi-AZ and read replicas.
AWS · Intermediate level
Answer
Multi-AZ is for availability and failover; read replicas are for read scaling and sometimes DR. Classic Multi-AZ standby is not for reads, while replicas are usually asynchronous and can lag.
Technical explanation
Read replica lag must be monitored before sending user-facing reads to replicas.
Database service choice depends on data model, access patterns, consistency requirements, operational burden, scaling model, and failure tolerance.
Managed databases still require customer ownership of schema, indexes, queries, IAM/network security, backups, upgrades, and restore validation.
Production data design should include encryption, private networking, least-privilege access, monitoring, backups, failover testing, and cost controls.
Hands-on example
1. Create the database/cache in private subnets with encryption, least-privilege security groups, backup/retention settings, and monitoring enabled.
2. Run a representative workload test and capture latency, throughput, connection count, CPU, memory, I/O, and errors.
3. Test the failure path: failover, replica lag, cache loss, throttling, or restore depending on the service.
4. Write the operational runbook covering access, backup, scaling, alarms, and rollback.
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